The present invention relates to a needle loom with an automatic change of the weft thread.
In textile machines, fabric formation takes place through mutual interlacing of a plurality of warp and weft threads suitably engaged by respective weaving members.
It is known that the textile machines called needle looms comprise one or more forming heads designed to form the textile product at which interlacing occurs between the warp threads coming from respective beams installed on a rack called “creel”, and the weft threads unwound from respective bobbins mounted on a creel dedicated thereto and fed from suitable devices. The needle looms are used to manufacture textile products of an indefinite length but having reduced widths, in the order of few centimeters, such as ribbons, tapes or laces, shoulder straps, etc.
Each forming head substantially comprises a bearing plate defining the forming plane of the textile product, at least one pair of heddle frames designed to alternately raise and lower the warp threads fed to the bearing plate, a sickle bringing one or more weft threads between the warp threads in a direction transverse to the warp threads themselves, a needle designed to retain the weft threads before the latter are harnessed between the warp threads by effect of the heddle frame motion, and a reed that, after each passage of the sickle, compacts the weft threads on the already formed textile product. Suitable means disposed downstream of the forming station keep the textile product under tension and allow the same to come out of the loom.
Known in the art are needle looms capable of feeding two or more weft threads, of different colors or materials, to the sickle, and to select which of said threads must be included in the fabric at each passage of the sickle itself. Needle looms of this type allow ribbons with multi-colored transverse bands to be manufactured, for example.
For the purpose, the looms of the known art are provided with a particular guide device that is placed upstream of the sickle and enables each of the weft threads to be moved vertically between an active position at which it is hooked by the sickle, and a passive position at which the sickle is not able to intercept said weft thread.
This device is located close to the bearing plate and the reed and comprises as many movable guide elements as the weft threads. Each guide element is provided with an eye through which a weft thread passes before reaching the sickle. Each guide element is vertically movable usually between a lower position, an intermediate position and un upper position. The sickle is provided with a hook in which the weft thread engages when the latter is brought to the intermediate position by a movable guide element while the other elements are at one of the end positions.
Movement of the guide elements in accordance with the known art is obtained through complicated motion-transmitting mechanisms connected with the main drive shaft of the needle loom and capable of converting the periodic motion of the shaft into distinct movements that are however correlated with the individual guide elements.
The motion-transmitting mechanisms of known type are formed of mechanical transmissions and/or magnetic actuators capable of hooking or releasing one of the movable guide elements, based on the angular work phase of the drive shaft.
As a consequence of the above, in most of the known needle looms, the law of motion of the movable guide elements cannot be varied, unless the whole motion-transmitting mechanism is fully designed again.
Also known are needle looms enabling movement of the guide elements to be changed; but in this case the motion-transmitting mechanisms must be disadvantageously physically modified through replacement of parts of them or mounting of said parts according to different configurations for example, in order to pass from a pattern to another.
In any case, all needle looms of known type do not enable the law of motion of the guide elements to be changed and therefore the distribution of the weft threads in the fabric to be modified during working.